Medical devices have been used to deliver therapeutic agents locally to the body tissue of a patient. For example, intravascular stents comprising a therapeutic agent have been used to locally deliver therapeutic agents to a blood vessel. Often such therapeutic agents have been used to prevent restenosis. Examples of stents comprising a therapeutic agent include stents that comprise a coating containing a therapeutic agent for delivery to a blood vessel. Studies have shown that stents having a coating with a therapeutic agent are effective in treating or preventing restenosis.
Even though medical devices having a coating with a therapeutic agent are effective in preventing restenosis, many coated medical devices, in addition to being coated with a therapeutic agent, are also coated with a polymer. The benefits of using a polymer in such coatings include easier loading of therapeutic agents onto the surface of a medical device and the ability to control or regulate the rate of release of the therapeutic agent.
However, the use of polymers in medical device coatings can also have some disadvantages. For example, depending on the type of polymer used to coat the medical device, some polymers can cause inflammation of the body lumen, offsetting the effects of the therapeutic agent. Additionally, some polymers may also cause thrombosis.
Accordingly, there is a need for coatings for a medical device that prevent or at least reduce the disadvantages associated with polymer coatings, such as inflammation caused by contact with the body lumen. Moreover, there is a need for a coating for medical devices that can control or regulate the release rate of a therapeutic agent without the use of polymer coatings. There is also a need for methods of making such medical devices.